Friday, March 03, 2006

Largest, Oldest Female Adapted To Cold

From Bruce Bower at Science News:
A 260,000-year-old partial skeleton excavated in northwestern China 22 years ago represents our largest known female ancestor, according to a new analysis of the individual's extensive remains.
This ancient woman puts a modern twist on Stone Age human evolution, say Karen R. Rosenberg of the University of Delaware. The fossil individual's large size and the apparent adaptation of her body to cold conditions are "consistent with the idea that patterns of human anatomical variation that we see today have deep evolutionary roots," Rosenberg asserts.

Although the woman belonged to the Homo genus, her species is uncertain. Now known as the Jinniushan specimen, she stood roughly 5 feet, 5-1/2 inches tall and tipped the scales at 173 pounds, the three anthropologists estimate. The only Stone Age Homo woman known to have approached that size weighed an estimated 163 pounds. Her partial skeleton came from a 100,000-year-old Neandertal site in France.

The Jinniushan specimen's size reflects her membership in a population that, as an adaptation for retaining heat in a cold climate, evolved large, broad bodies with short limbs, a shape similar to that of near-polar populations today. The work will be published in an upcoming issue of the Proceedings of the National Academy of Sciences.

The large estimated brain size of the Chinese fossil supports a current theory of mid–Stone Age brain expansion in Homo species, the researchers say. Earlier analyses of other fossils' skulls and lower-body bones—not including multiple bones from single individuals—had indicated that, between 1 million and 200,000 years ago, the Homo lineage peaked in body size and displayed considerable brain growth relative to body size.